The Windows 11 update always fails due to error code 0xc1900101.

Hello @xyyang

Error 0xC1900101 is a generic Windows Setup rollback code and, according to Microsoft, it usually indicates a driver compatibility issue.

From your screenshot, the device has successfully installed earlier Windows 11 Insider builds, but the upgrade to Windows 11 25H2 is repeatedly rolling back.

I would first update the BIOS/UEFI and chipset, storage, graphics, network and Bluetooth drivers directly from the PC/motherboard manufacturer's support site. Also disconnect nonessential USB devices and temporarily remove third-party antivirus/VPN/security software before trying the upgrade again. Microsoft specifically recommends checking drivers and unnecessary peripherals for 0xC1900101 failures.

More importantly, we need the extended error code to determine exactly where Setup is failing. For example:

0xC1900101-0x20017

0xC1900101-0x30018

0xC1900101-0x40017

After the next failed attempt, check:

C:$WINDOWS.~BT\Sources\Panther\setuperr.log

C:$WINDOWS.~BT\Sources\Panther\setupact.log

*C:$WINDOWS.~BT\Sources\Rollback*

Microsoft also recommends SetupDiag for identifying the specific reason an upgrade rolled back.

If you can share the complete 0xC1900101-0xXXXXX code or the relevant section of setuperr.log, we can usually identify which driver or Setup phase is causing the 25H2 upgrade to fail.

Please "Accept the Answer" if this information helped you. This will help us and others in the community as well.